1. Field of the Invention
The invention relates to an arrangement for a circular comb, employed for processing fibers supplied in the form of a fiber band and rotatable about an axis of rotation, with at least two arrangement sections arranged behind one another in the circumferential direction of a circular cylindrical mantle surface rotating about the axis of rotation, wherein the engagement section that engages first the fiber band upon rotation of the circular comb about the axis of rotation provides a lesser combing effect than at least one of the follower sections passing subsequently through the fiber band; a circular comb provided with such an arrangement; and a comber having such a circular comb.
2. Description of the Related Art
Circular combs provided with arrangements of the aforementioned kind are used during the processing or finishing of fibers in combers for separating short fibers and neps as well as shell parts from the already carded raw fiber material. In this connection, the combing process makes the staple, i.e., the fiber length of the raw fiber material, more uniform. For this purpose, the comber is arranged conventionally between the carding machine and the draw frame.
In the comber a fiber tuft of a fiber band comprised of preferably already carded fibers is fused to a fiber band of already combed fibers and secured by nippers, and the teeth of the circular comb then pass through the fiber tuft. The entire process of engagement of the comb teeth in the fiber tuft, the combing, the fusing up to the point when the circular comb engages a fiber tuft that is newly supplied to the nippers is referred to as xe2x80x9ccomb playxe2x80x9d.
Conventional circular combs comprise a substantially cylindrical support body wherein the comb extends over a portion of the circumference of the cylinder. During operation of the comber the circular comb rotates about the cylinder axis and is arranged relative to the nippers such that the teeth of the comb can pass through the fiber tuft secured by the nippers, but such that the support body upon further rotation of the circular comb does not hinder the fusing of the combed fiber tuft. Conventionally, the circular comb for this purpose is configured such that a base body is mounted on the cylindrical support body which expands the support body in the radial direction and on which the actual circular comb arrangement is secured.
In the development of circular combs, arrangements with round needles were initially employed. With such circular combs a processing speed of 100 to 110 comb plays per minute could be achieved while maintaining a satisfactory combing effect. By replacing the circular needles with all-steel sawtooth arrangements an increase of the processing speed up to 350 comb plays per minute could be realized without impeding the combing effect. A further increase of the processing speed could be obtained without affecting the actual combing results by a further development of conventional circular combs disclosed in DE 43 26 205 C1, in which a channel is arranged between the arrangement and the support body for preventing dynamic pressure in front of the arrangement.
When using the circular combs described in the aforementioned document, it was initially observed that the fibers to be processed were damaged at high processing speeds. For eliminating these shortcomings, arrangements of the aforementioned kind were suggested with which a damage-poor engagement of the arrangement via the engagement section in the fiber tuft can be achieved while with the follower sections the desired combing result can be produced. When using arrangements formed of sawtooth wire strips, the higher combing effect of the follower sections in the known arrangements is achieved by a corresponding reduction of the spacing between the tooth tips of the sawteeth of the follower sections in comparison to the spacing between the tooth tips of the engagement section. With this further development of the arrangements it was possible to obtain up to 400 comb plays per minute with a satisfactory combing effect, but it was found that at these high processing speeds the time still available after the actual combing process is no longer sufficient for fusing the combed or still to be combed fiber tuft with a fiber band comprised of already combed fibers. Accordingly, in a subsequent developmental step a shortening of the arrangement length of initially more than 120xc2x0 in the circumferential direction of the circular comb to less than 110xc2x0 in the circumferential direction of the circular comb was proposed in order to thus provide even at high processing speeds still sufficient time for fusing. However, it was found that in the last disclosed development of circular combs a considerable impairment of the combing result was observed.
It is an object of the present invention to provide an arrangement of the aforementioned kind which, when used even at high processing speeds of 400 comb plays per minute or more, provides still sufficient time for fusing the combed fiber tuft with a fiber band comprised of already combed fibers while guaranteeing a satisfactory combing result.
In accordance with the present invention, this is achieved in that at least one of the follower sections in the circumferential direction has a greater length than the engagement section.
This invention is based on the recognition that a gentle and damage-poor engagement of the circular comb arrangement in the supplied fiber tuft can be ensured already when the engagement section extends only over a very small angle in the circumferential direction of the circular comb so that, while guaranteeing a damage-free engagement of the circular comb arrangement via the comparatively short engagement section, a great arrangement length for the more effective arrangement sections is provided without increasing thereby the total length of the arrangement in the circumferential direction. Overall, by using an arrangement which in the circumferential direction of the circular comb extends about an angle of less than 110xc2x0, preferably less than 100xc2x0, more preferred approximately 90xc2x0, a satisfactory combing results can be obtained without damage of the fibers to be processed. With this, even at high processing speeds of 400 comb plays per minute or more sufficient time is still made available for the process of fusing.
With the circular comb arrangement according to the invention an especially good combing result can be achieved with an especially minimal arrangement length while preventing excessive fiber damage, when the arrangement has at least two, preferably at least three, follower sections wherein each has an increased combing effect and/or a greater length than the preceding follower sections, respectively, the engagement section.
In this context, for an arrangement extending over an angle of less than 110xc2x0, more preferred approximately 90xc2x0, a satisfactory combing result without damage of the fibers upon engagement of the arrangement in the fiber tuft is possible when the ratio of the length of the engagement section to the last follower section is in the range of 1:2 to 1:4.
When using an arrangement comprised of four arrangement sections arranged one after another in the circumferential direction for an arrangement length extending over an angle of approximately 90xc2x0, an especially good combing result can be achieved when the lengths of the individual arrangement sections, starting at the engagement section in a direction toward the last follower section, have a ratio of 1:1.2(xc2x10.1):1.8(xc2x10.5):3(xc2x12). The values given in parentheses represent the possible deviations of the especially preferred values given without parentheses.
As has already been explained in detail, when using high performance combers it is especially advantageous when at least one of the arrangement sections, preferably however all arrangement sections, comprise a plurality of sawtooth wire strips arranged adjacent to one another in the direction of the axis of rotation. For such arrangements a higher combing effect of the follower sections can be achieved in comparison to the engagement section when the spacing between the tooth tips of the sawtooth wire strips of the engagement section is greater than that between the tooth tips of the sawtooth wire strips of at least one of the follower sections, preferably of all follower sections.
For an arrangement extending in the circumferential direction of the circular comb over an angle of approximately 90xc2x0, an especially high combing effect is ensured while a damage-poor engagement of the arrangement is guaranteed, when the ratio of the spacing between the tooth tips of the engagement section to that between the tooth tips of the last follower section is in the range of 1:0.2 to 1:0.4, preferably approximately 0.35.
In the last described embodiment of the invention using four arrangement sections arranged one after another, an especially good combing result is obtained when the spacings between the tooth tips of the arrangement sections, starting with the engagement section in a direction toward the last follower section, is 1:0.7(xc2x10.2):0.55(xc2x10.1):0.3(xc2x10.1), wherein the values given in parentheses represent the possible deviations of the preferred values given without parentheses. In this context, the spacing between the tooth tips of the engagement section in the stretched arrangement, i.e., before adaptation of the corresponding sawtooth wire to the circular cylinder mantle surface of the base body, is preferably approximately 4 to 5 mm, more preferred approximately 4.47 mm.
In addition, or as an alternative, to the last described embodiment of the invention with changing spacings between the tooth tips of the individual arrangement sections, respectively, a variable tooth division, a higher combing effect of the follower sections in comparison to the engagement section can also be achieved in that the width of the arrangement grooves between the sawtooth wire strips of the engagement section extending in a direction parallel to the axis of rotation is smaller than the width of the arrangement grooves of at least one of the follower sections, preferably of all follower sections. This increase of the combing effect of the follower sections can be achieved, for example, in that the base width of the sawtooth wire strip of the follower sections, while maintaining identical blade width, is increased in comparison to the sawtooth wire strips forming the engagement section. In an especially preferred embodiment of the invention, the base width of the sawtooth wire strips forming the engagement section is approximately 0.8 mm, while the base width of the successively arranged follower section is 0.65, 0.6 or 0.5 mm for identical blade width.
A further additional or alternative possibility for increasing the combing effect of the follower sections in comparison to that of the engagement section resides in that the sawteeth of the engagement section are provided with a smaller breast angle than that of at least one of the follower sections, preferably of all follower sections. In this connection, the breast angle of the sawtooth wire strips, forming the engagement section, in the stretched state, i.e., before application onto the base body of the circular comb, is preferably approximately 30xc2x0, while the breast angle of the sawtooth wire strips, forming the follower sections, in the stretched state is approximately 35xc2x0, 40xc2x0 and also for the last follower section is still 40xc2x0. In other applications, such as, for example, the combing of short staple cotton, for which only a minimal combing effect is desired, the breast angle of all follower sections as well as the breast angle of the engagement section can be 30xc2x0. On the other hand, when processing long staple material, the breast angle of the last follower section can be up to 55xc2x0 wherein the breast angle of the other follower sections can also be increased accordingly.
Finally, in the circular comb arrangements according to the invention it may also be provided that the tooth height of the sawteeth of the engagement section is greater than that of the sawteeth of at least one follower section, preferably of all follower sections.
In an especially advantageous embodiment of the invention all of the aforementioned measures for increasing the combing effect are applied in the embodiments of the follower sections, wherein expediently all arrangement sections have approximately the same arrangement height for maintaining a disturbance-free operation of the comber.
As can be taken from the afore disclosed description of the arrangements according to the invention, a circular comb produced accordingly has a substantially circular cylindrical support body, a base body extending over a portion of the cylinder circumference and expanding the support body in the radial direction, as well as an arrangement mounted on the base body, wherein the arrangement comprises at least two arrangement sections arranged one after another in the circumferential direction and having combing effects that differ from one another, wherein at least one of the follower sections passing through a fiber band after the engagement section has a greater length in the circumferential direction than the engagement section.